Only inject the HTML titlebar into toplevel frames.

chrome/renderer/extensions/app_window_custom_bindings.cc

Index: chrome/renderer/extensions/app_window_custom_bindings.cc
diff --git a/chrome/renderer/extensions/app_window_custom_bindings.cc b/chrome/renderer/extensions/app_window_custom_bindings.cc
index de61374c83de0e10be4d53002d81c6467132a90a..65473b75021d042ad89236996efa62a7a84c0725 100644
--- a/chrome/renderer/extensions/app_window_custom_bindings.cc
+++ b/chrome/renderer/extensions/app_window_custom_bindings.cc
@@ -27,9 +27,12 @@ class DidCreateDocumentElementObserver : public content::RenderViewObserver {
   }
 
   virtual void DidCreateDocumentElement(WebKit::WebFrame* frame) OVERRIDE {
-    v8::HandleScope handle_scope;
     DCHECK(frame);
     DCHECK(dispatcher_);
+    // Don't attempt to inject the titlebar into iframes.
+    if (frame->parent())
+      return;
+    v8::HandleScope handle_scope;
     ChromeV8Context* v8_context =
         dispatcher_->v8_context_set().GetByV8Context(
             frame->mainWorldScriptContext());